Abstract

The first population of the leaf beetle, Diorhabda elongata, to be tested as a saltcedar biocontrol agent, originated in the northwest corner of China, Xinjiang Province, near the town of Fukang. This insect population enters a state of dormancy, known as diapause, in response to daylengths shorter than about 14.5 hours of light. This diapause response results in a shutdown of the reproductive systems of both male and female beetles, as well as a departure of adults from the host plant and movement to the leaf litter. With this photoperiod requirement the beetles cannot achieve two full generations per year at latitudes below the 37th parallel and will probably fail to thrive in the southern range of saltcedar. For this reason we are testing new populations of D. elongata collected from a number of sites in Europe, Asia and Africa. These populations reproduce under shorter daylengths and will be compatible with the southern range of saltcedar.

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